The yetzer hara has no power or authority on that person, but just through his eyes

(About Yoseph HaTzadik and Potiphar wife)
Not only was she relentlessly working to making him yield to her advances, but her heart was also set on getting him to somehow to look at her. The Midrash tells us that she even positioned a metal pointed roasting spit at his neck to coerce him to look at her. But her efforts were in vain.

The Medrash makes the point in several places, that the severest of his trials was in fact to avoid looking at her. Yet he stood firm. That mighty hero, Yosef Hatzadik, never once glimpsed at her. After twelve years, his purity intact, he emerged from prison and was rushed to stand before Pharaoh.

See how wonderful these words are! The prohibition in the case of illicit relations is likened to the case of a Nazarite, where, even though the essence of the prohibition involves only the drinking of wine, the Torah forbids him anything which has any connection to wine.

By applying this principle to the area of illicit relations, the Sages prohibited anything partaking of the nature of fornication, or anything approaching it, regardless of the particular avenue of approach, whether that of deed, sight, speech, hearing, or even thought.

Deed: Namely touching or embracing and the like. This has already been mentioned and there is no need to expand upon it.

Sight: Our Sages of blessed memory have said: "One who counts coins from his hand to hers in order to gaze at her will not be cleansed from Gehinom" (Berachot 61a). And, "Why did the Jews of that generation require atonement? Because they fed their eyes on impurity" (Shabbat 64a). Also, they said, "It is written in the Torah, 'And keep yourself from every evil thing,' meaning a man should not gaze upon a beautiful woman, even if she is single, nor upon a married woman, even if she is ugly" (Avodah Zarah 20a).

Speech: It is explicitly stated: "One who converses at length with a woman draws evil upon himself" (Avot, 1:5).

Hearing: "Listening to a woman's singing is considered licentiousness" (Berachot 24a).

Also talking about and hearing licentious matters is considered "fornication of the mouth and ear." On the verse, "Let there not be seen with you a thing of nakedness," our Sages said this means nakedness of speech and the uttering of obscenities (Yerushami Terumot 1:4). Also, "Everyone knows why a bride goes to the wedding canopy, but anyone who speaks obscenely concerning it, even a decree of seventy good years is converted to evil (Shabbat 33a). And, "Even a casual conversation between a man and his wife is held up to him at the time of Judgment (Chagigah 5b).

Thought: Our Sages of blessed memory have already said that the verse, "Keep yourself from every evil thing," means that a man should not think lewd thoughts in the daytime and come to impurity at night (Avodah Zara 20b). Also, "The thoughts behind the sin are worse than the sin itself" (Yoma 29a).

We see then that all of one's faculties must be clean of licentiousness and anything relating to it.